Method of making steel-rule type piercing and blanking dies



Oct. 13, 1964 G.

METHOD OF MAK Oct. 13, 1964 G. WHITECOTTON 3,152,492

METHOD OF MAKING STEEL-RULE TYPE PIERCING AND BLANKING DIES Filed Jan. 3, 1962 5 Sheets-Sheet 2 IN VENTOR. Gen wow 5 M/raomm Arrow/25.

G E. WHITECOTTON KING STEEL-RULE TYPE PIERCING METHOD OF MA AND BLANKING DIES 3 Sheets-Sheet 3 Oct. 13, 1964 Filed Jan. 3, 1962 INVENTOR. Gem pow 15. Mi /acorn,

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United States Patent 3,152,492 METHQD 0F MAKING STEEL-RULE TYPE PHERCENG AND BLANKING DIES Graydon E. Whitecotton, 910 /2 N. Washington St, Ko'komo, Ind. Filed Jan. 3, 1962, Ser. No. 164,133 9 Claims. (Cl. 76107) This invention relates to a method and apparatus for making steel-rule type piercing and blanking dies, and to novel die elements produced thereby.

Dies of this type comprise a pair of companion dies which, conventionally, are used in master die sets or holders having guided top and bottom die shoes, with the respective dies located and retained on the top and bottom shoes by means of locating dowels and retaining screws. In the past, it has been necessary for the tool room or tool shop building such dies to build them on the same master die sets on which the dies will be used in production or on similar master die sets which have the same screw and dowel pattern as the production die sets. In most cases, moreover, it has been necessary at at least some stage of the die making method to have the dies or die stock mounted in the die set and the die set installed in operative relation in a punch press.

These requirements of prior methods have made it necessary for the die maker to have in hand either the actual production master die sets or duplicates of them, which is especially burdensome in the case of tool shops serving several customers who may use different die sets or diilerent dowel and screw locations. Such requirements also tie up the use of punch presses which would otherwise be available for production.

It is an object of the present invention to provide a method of producing steel-rule type piercing and blanking dies which does not require construction on a master die set and, instead, permits the use of a simple inexpensive jig, and which method will produce dies of high quality that will hold close tolerances in production, will pierce and blank sheet metal in thick gauges up to one-half or even one inch thickness, will produce high quality, burrfree stampings and will operate over long production runs.

The method in accordance with the invention is generally as follows: A steel-rule die is prepared on a die block provided with locating means, e.g., dowel holes, to locate the die in the die set. A punch blank is mounted on a punch plate which has corresponding locating means for locating the punch in the die set, and the punch is overlaid with an adherent impressionable layer of hardenable resin, such as epoxy paste. The die and punch assembly are then assembled, and by the use of their locating means and a cooperating jig are accurately located in exactly the same relative positions they will have in the die set, with the shearing elements of the die impressed in the soft layer of resin on the punch blank. The resin is then hardened, with the die and punch so assembled, to capture in the resin layer on the punch blank an exact and precise impression of the shearing elements of the die. The punch blank is then removed and sawed and filed to form a punch according to the impression in the resin.

This latter operation desirably includes cutting the blank to form a clearance suitable to the character and thickness of the material to be pierced or blanked by the dies in use. In order to check such clearance, a second layer of hardenable plastic is applied to the punch and overlying its edges, the die and punch are reassembled on the jig, again in the same relative positions they will have in use and with the face of the punch telescoped past the working edges of the shearing elements. With the parts so assembled, the second layer of resin is hardened to form at the edges of the punch a thickness of hardened resin corresponding to the clearance. The parts are then separated and this clearance thickness of resin is directly measured.

The punch, with proper clearance and ordinarily after removing the resin and hardening the metal, is assembled to its punch plate and the dies are then mounted in the master die set for production operation.

Epoxy resins have been found especially useful since they set to a hard adherent layer at normal temperatures in reasonable times. They preserve an accurate impression of the die elements, and they are compatible with normal sawing, filing and other stock-removal procedures used to form the punch. But other impression resins may be used which permit making an impression while in soft state and which can then be hardened to preserve the impression for use in forming the punch.

Other objects and features of the invention will be evident from the preferred embodiment shown in the accompanying drawings to illustrate the invention. In such drawings:

FIG. 1 is an isometric exploded view showing a steel rule shaped to the outline of a stamping to be produced, and a die block slotted to receive the steel rule to form a die;

FIG. 2 is an isometric view of a die formed from the parts shown in FIG. 1;

FIG. 3 is an isometric view of an assembly jig suitable for use in the method of the invention;

FIG. 4 is a longitudinal sectional view showing a punch blank assembly mounted on the jig of FIG. 3 and with the die of FIG. 2 assembled thereto with its shearing elements impressed in the layer of resin on the punch blank;

FIG. 5 is a fragmentary section showing punch blank after removal of stock therefrom to form the punch die with proper clearance at its periphery;

FIG. 6 is a view similar to FIG. 4 with the punch covered with a second layer of resin and with the upper die in position to be lowered onto the lower die to check the clearance;

FIG. 7 is a fragmentary view showing the second resin layer after it has been hardened for the purpose of checking the clearance; and

FIG. 8 is a front isometric exploded view of a master die set with dies according to the invention mounted therein.

The master die set shown in FIG. 8 comprises a top shoe 10 having guide sleeves 12 at its rear corners, and a bottom shoe 14 having guide posts 16 at its rear corners for the reception of the guide sleeves 12, so that the upper shoe ill will be guided for accurate translatory movement perpendicular to the lower shoe 14.

A still-rule die 20 is mounted on the upper shoe 10 and is located and retained by means of locating dowels 11 and retaining screws 13 received in dowel holes 22 and screw holes 24 in the die plate of the die 20. A punch die 30 is mounted on the slug rails 18 on the lower shoe 12 and is located and retained on the shoe by means of dowels 15 and retaining screws 17 received respectively in dowel holes 32 and screw holes 34 in the base plate of the die 30. The positions of the dowels and screws will be in a predetermined pattern suitedto the various types of dies to be used on the die set, and will normally be one of several conventional patterns. Further, the dowels 11 and 15 of the two shoes will normally be in accurate vertical alignment and the two dies 2% and 30 will be located for relative vertical movement toward and away from each other by their interengagement with such aligned dowels.

In the method of the invention, the construction of accurately interrelated dies 20 and 30 for use in the die set 10-14 requires only an accurate knowledge of the loca tions and spacing of the dowels 11 and 15, and of the 3 retaining screws 13 and 17, and the use of the die set itself is not required during construction of the dies.

The upper die is made first, and this may be done by various known techniques. The die 29 shown in FIGS. 1 and 2 comprises a die block 21 of plywood material, 4 inch thick, preferably a high-density material made especially for this purpose, such as that available on the market under the trademark Hy-Du-Lignum. For heavier dies, 1-inch thick material may be used. The exact outline of the desired stamping is laid out on the surface of the die block 21, and a slot 23 is then precision jigsawed in the block along the layout lines, with the lines defining one edge of the slot, in this case the inner edge. The width of the slot is made to receive the steel rule with a light press fit. The slot is preferably interrupted to leave bridges integrally connecting the center portion to the outer or marginal portion of the die block, but may be continuous if desired. The block is also precision bored for the reception of piercing punches 28 shown in FIG. 2, and is precision bored to provide dowel holes 22 and screw holes 24 in proper relation to the slot 23 and to match the dowel 11 and screw 13 location of the upper shoe of the master die set or holder on which the die 20 is to be used.

A steel rule die blade 26 is then formed from steel rule of a thickness to have a light press fit in the slot 23. Conveniently the rule may be either 8-point or 10-point rule .112 or .140 inch thickand may be either 1%. or 1 /8 inches wide. It is notched at the rear with notches 27 to straddle the bridges 25 of the die block 21. The shaped rule 26 is then hardened, and the hardened die rule is then inserted in the slot 23. The resulting die is then checked for accuracy and, if errors are found, is ground or adjusted to the proper dimensions and tolerances. The steel rule used may be of the standard cross-section, shown in FIGS. 1 and 2, with a 45 bevel on its working edge. The formed die blade 26 is normally ground to remove the sharp edge and to provide a narrow fiat land 29 as shown in FIG. 5. The width of such land 29 will vary with the character and thickness of the material to be blanked, and should be wide enough to exert the necessary shearing pressure, but narrow enough to at least slightly impress itself into such material in order to interlock therewith to avoid lateral bending stress. The piercing elements 28 are also inserted in the block 21, and the accuracy of their positions checked. The stamping which will be produced will have the same dimensions as the die 20, and this must be properly constructed with an accuracy suited to the tolerances required in the finished stamping.

The companion die 30 is next made, and for this purpose the already completed die 20 is used in accordance with the method of the invention.

A male dieor punch-blank 31 is mounted on a dieor punch-plate 33 by means of dowels 35 and screws 36, and the blank 31 is positioned relative to the locating dowel holes 32 and retaining screw holes 34 so that it will underlie the die 20 when the two dies are assembled with the dowel holes 22 and 32 in alignment. The punch blank is then coated with an impressionable layer 38 of a raw resin such as epoxy resin. The resin is applied in uncured state and is desirably allowed to partially cure to a soft impressionable state. The resin layer may be of the order of inch thick.

The assembly jig 45) shown in FIGS. 3, 4 and 6 comprises a base plate 42 in which are accurately mounted two perpendicular dowel posts 44 which precisely correspond in size and relative location with the dowel pins 11 and 15 of the master die set 1014 on which the dies 20 and 30 are to be used.

The punch blank 31, mounted on the punch base plate 33 and bearing the soft impressionable resin layer 38, is assembled to the jig 40 with the base plate 33 resting on the base 42 and located by engagement of the dowel posts 44 in the dowel holes 32. The shearing elements of the die 20 are coated with wax or other parting elements to prevent adhesion by the resin material, and the complete ie 20 is then assembled to the jig 40, by engaging the dowel holes 22 over the dowel posts 44 with the working edges 29 of the steel rule projecting downward. The die 20 is then lowered on the dowel posts 44 to bring the working ends or edges of its shearing elements 26 and 28 into engagement with the soft resin layer 38, and the die 20 is manually pressed downward to cause such elements to impress themselves in the soft resin material, as shown in FIG. 4. The assembly is then allowed to stand, at room temperature with the die 20 pressed by its own weight into the soft resin, until the resin is completely cured to a hard state.

The dies 20 and 39 are then disassembled from the jig, and the punch blank 31 bearing the impressions of the die 26 in its resin layer 38 is removed from the base plate 33 and is sawed and filed or otherwise machined to the hardened impression of the shearing blade 26, and is bored to form openings at the impressions of the piercing elements 23, and thus to form a punch 39. Further, additional material is removed to provide proper clearance between the dies. In FIG. 5, the original dimension of the punch blank 31 is shown in dotted lines, and the final dimension of the punch 39 shown in full lines. The finished edge face 35 of the punch is spaced slightly inward from the position of the steel rule die blade 26 to provide clearance. The amount of such clearance will be chosen to suit the character and thickness of the material to be blanked, in accordance with conventional criteria.

For the purpose of checking the amount of such clearance, the trimmed punch 39 is re-mounted on the plate 33 and is given a second thin coating 46 of epoxy resin which is partially cured to a semi-solid state, and the dies 29 and 30 are again assembled on the jig I-fi as shown in FIG. 6. When the die 20 is lowered toward the die 30, the shearing elements 26 and 28 will telescope past the punch 39 and this will deform the resin layer 46 into the narrow clearance spaces between the die elements. Again the dies are allowed to stand until the resin 46 has hardened, and are then disassembled. The clearance will now be captured in a thin layer 4-7 of the resin 46 overlying the side face 35 of the punch 39 as shown in FIG. 7, and the clearance can be checked by measuring the thickness of this layer, as indicated by the arrows on FIG. 7.

If the clearance is found satisfactory, the punch 39 is then disassembled, its resin layers 33 and 46 are removed, and the punch 33 is hardened and then re-mounted on the plate 33 to form the finished punch die 3'3.

The dies 2t] and 3t) are then ready for use, and are now, for the first time, to be mounted in the master die set 13-14- in the relationship shown in PEG. 8. The die set containing the dies 29 and 30, together with conventional stripper material or mechanism, may then be mounted in a punch press for production operation.

With reasonable care, the method set forth produces steel-rule type dies of high accuracy and true alignment, which have been found to hold tolerances as close as those of conventional (and more expensive) all-steel dies, to produce stampings free from burrs, to be capable of piercing and blanking sheet steel up to one (1) inch thick and of producing hundreds of thousands of stampings. Moreover, the method eliminates all need for using the master die set in the construction of the dies and greatly enlarges and facilitates the work which can be handled by independent tool and die shops.

I claim as my invention:

1. The method of making steel-rule type dies adapted for use in die holders having aligned locating dowels, comprising (a) forming a steel-rule first die having shearing elements set in a die block provided with correspondingly located dowel holes for positioning said die in its die holder,

([1) replaceably mounting a punch the blank on a punch die plate provided with correspondingly located dowel holes,

(0) providing on said punch blank an adherent impressionable soft layer of hardenable resin, such layer being of substantial thickness adapted to form a die element impression defined by edge faces of substantial width in the direction of the thickness of the layer,

(d) assembling on a jig having locating dowel pins,

(1) said punch die plate with said resin-carrying punch blank mounted thereon, and (2) said steel-rule die,

(e) with said punch plate and die aligned by engagement of said jig dowel pins in the die dowel holes and with the shearing elements of said first die impressed in said soft resin layer, under a light pressure sufficient to press the shearing elements deeply into the soft resin layer and bring the edges of such elements substantially to the metal face of the punch die blank and less than sufiicient to make any substantial impression in such metal face,

( hardening said resin layer with the parts so assembled, to form a hardened impression of said first die defined by edge faces of substantial Width in the hardened resin on the punch blank,

(g) removing the punch blank from the assembly With the die-element impression in the hardened resin layer thereon,

(h) machining the punch blank to said hardened impression to form a punch to match said first die, and

(i) remounting said punch on said punch die plate to form a second die matching the first die.

2. The method defined in claim I, with the addiiton of,

(a) mounting said first and second dies in a die-holder set with the die dowel holes received over the aligned dowels of the die-holder set to locate the dies in operative alignment.

3. The method defined in claim 1 in which,

(a) in assembling said punch die plate on said jig, the same is located thereon by engagement of the dowel holes of said die plate over the jig dowel pins, said pins being arranged to project perpendicularly above said punch blank,

(b) in assembling said steel-rule die on said jig, the same is positioned in face-to-face relation with the punch blank, and is located by slidable engagement of its dowel holes over the said perpendicular jig dowel pins,

(0) and said steel-rule die is slidably moved on the dowel pins toward said punch blank to impress said shearing elements in said soft resin layer by pressure not substantially exceeding manually-applied and gravity pressure on the steel-rule die.

4. The method defined in claim 1 in which said machining removes additional material inward of said hardened impression to provide clearance between said die and punch.

5. The method of making steel-rule type dies having means for locating the same in die holders, comprising (a) forming a steel-rule first die having shearing elements set in a die block,

(b) providing a punch die blank with an adherent impressionable soft layer of hardenable resin, such layer being of substantial thickness adapted to form a die element impression defined by edge faces of substantial width in the direction of the thickness of the layer.

(0) assembling said first die and said die blank in the same alignment they are to have in the die holders and (d) with the shearing elements of said first die impressed in said soft resin layer under a light pressure sufiicient to press the shearing elements deeply into the soft resin layer and bring the edges of such elements substantially to the metal face of the punch die blank and less than sufficient to make any substantial impression in such metal face,

(e) hardening said resin layer with the parts so assembled, to form a hardened impression of said first die defined by edge faces of substantial width in the hardened resin on the punch blank,

(f) removing the punch blank from the assembly with the die-element impression in the hardened layer thereon, and

(g) machining the punch blank to said hardened impression to form a punch to match said first die.

6. The method defined in claim 5, in which (a) said layer of hardenable resin is an incompletely cured layer of self-curing epoxy resin, and

(b) said layer is hardened by allowing the same to stand.

7. The method defined in claim 5 with the addition of (a) coating the shearing elements of said first die with an adherence-preventing compound prior to impressing said elements in the resin.

8. The method defined in claim 5 in which the layer of hardenable resin has a thickness of the order of oneeighth inch.

9. The method of making matching dies having means for locating the same in die-holders, comprising (a) forming a female first die having shearing elements,

(b) providing a punch die blank with an adherent impressionable soft layer of hardenable resin, such layer being of substantial thickness adapted to form a die element impression defined by edge faces of substantial Width in the direction of the thickness of the layer,

(c) assembling said first die and said die blank in the same alignment they are to have in the die holders and (d) with the shearing elements of said first die impressed in said soft resin layer under a light pressure sufficient to press the shearing elements deeply into the soft resin layer and bring the edges of such elements substantially to the metal face of the punch die blank and less than sufiicient to make any substantial impression in such metal face,

(e) hardening said resin layer with the parts so assembled, to form a hardened impression of said first die defined by edge faces of substantial width in the hardened resin on the punch blank,

(f) removing the punch blank from the assembly with the die-element impression in the hardened layer thereon, and

(g) machining the punch blank to said hardened impression to form a punch to match said first die.

References Cited in the file of this patent UNITED STATES PATENTS 2,404,858 McLaren July 30, 1946 2,486,446 Teetor Nov. 1, 1949 2,495,221 Berlin Jan. 24, 1950 2,666,266 Sinhel Jan. 19, 1954 2,703,023 Sarno Mar. 1, 1955 2,939,347 Tobey June 7, 1960 3,000,237 Phillips et al Sept. 19, 1961 3,020,785 Leavesley et al Feb. 13, 1962 3,025,727 Smith Mar. 20, 1962 

9. THE METHOD OF MAKING MATCHING DIES HAVING MEANS FOR LOCATING THE SAME IN DIE-HOLDERS, COMPRISING (A) FORMING A FEMALE FIRST DIE HAVING SHEARING ELEMENTS, (B) PROVIDING A PUNCH DIE BLANK WITH AN ADHERENT IMPRESSIONABLE SOFT LAYER OF HARDENABLE RESIN, SUCH LAYER BEING OF SUBSTANTIAL THICKNESS ADAPTED TO FORM A DIE ELEMENT IMPRESSION DEFINED BY EDGE FACES OF SUBSTANTIAL WIDTH IN THE DIRECTION OF THE THICKNESS OF THE LAYER, (C) ASSEMBLING SAID FIRST DIE AND SAID DIE BLANK IN THE SAME ALIGNMENT THEY ARE TO HAVE IN THE DIE HOLDERS AND (D) WITH THE SHEARING ELEMENTS OF SAID FIRST DIE IMPRESSED IN SAID SOFT RESIN LAYER UNDER A LIGHT PRESSURE SUFFICIENT TO PRESS THE SHEARING ELEMENTS DEEPLY INTO THE SOFT RESIN LAYER AND BRING THE EDGES OF SUCH ELEMENTS SUBSTANTIALLY TO THE METAL FACE OF THE PUNCH DIE BLANK AND LESS THAN SUFFICIENT TO MAKE ANY SUBSTANTIAL IMPRESSION IN SUCH METAL FACE, (E) HARDENING SAID RESIN LAYER WITH THE PARTS SO ASSEMBLED, TO FORM A HARDENED IMPRESSION OF SAID FIRST DIE DEFINED BY EDGE FACES OF SUBSTANTIAL WIDTH IN THE HARDENED RESIN ON THE PUNCH BLANK, (F) REMOVING THE PUNCH BLANK FROM THE ASSEMBLY WITH THE DIE-ELEMENT IMPRESSION IN THE HARDENED LAYER THEREON, AND (G) MACHINING THE PUNCH BLANK TO SAID HARDENED IMPRESSION TO FORM A PUNCH TO MATCH SAID FIRST DIE. 